Use of engineered materials, such as wood composites and various plastics, including recyclable thermoplastic, such as high-density polyethylene (HDPE), is becoming increasingly popular in the construction industry. These uses encompass various horizontal and vertical applications that meet a range of present decorative and/or structural construction needs.
Structural members, such as joists, beams and the like, are currently available as wood lumber, a valuable yet limited resource with no recycling capability, as plastic lumber, and as reinforced or composite lumber. Composites often include wood fiber or fiberglass in a plastic matrix, or wood composites such as I-joist products having oriented strand board with micro-laminated top and bottom flanges.
Wood-containing products generally are sensitive to environmental conditions, such as the effect of moisture. Such sensitivity must be accounted for during design, installation and use. There are various recyclable thermoplastic products available which are generally less sensitive to environmental conditions, specifically to the effect of moisture, than wood and composite products. Design benefits follow accordingly.
HDPE resins are used in a variety of blow molding, rotational molding, and extruded applications for liquid food containers, automotive fuel tanks, and large volume drums. HDPE is widely known as the material of choice for recyclable milk containers. It is also widely used for pipelines for water or other solution distribution systems, and for liners for landfills, water, or other solution holding ponds.
U.S. Plastic Lumber Corporation provides a fiberglass reinforced HDPE product that is available in sizes and shapes of standard lumber. These plastic lumber products are typically heavy and contain fiberglass fibers that can quickly dull saw blades and drill bits of construction equipment used to size the materials. Other known HDPE I-joists contain hollow cores with wide flanges that are not conducive to easy cutting-to-dimension with standard construction tools, nor fit with standard fasteners.
Accordingly, there is a need for structural members, including joists, beams, posts and the like, that are preferably made of a weather-resistant recyclable material and that provide adequate structural performance while not being too heavy or large for practical use. In addition, there is a need for providing reinforced structural members that provide adequate structural performance and that can be worked with standard construction equipment without unduly dulling cutting blades and drill bits. There is a further need for such members to be available in either standard and custom sizes and ratings, on demand or as needed, and with the possibility of working the engineering tradeoff between strength and weight in use of engineered materials, such as HDPE.